Async/await simple example

Question

Im trying to understand the basics of async/await by creating a simple example. Im using Sqlite with an Async connection and I have a class like this:

public class User
    {
        public int Id { get; set; }
        public string Name { get; set; }
    }

Now lets say that I want to save a User to my UserTable and when the saving is done I wish to retrieve it.

public async ? SaveToDb()
        {
            _conn.CreateTableAsync<User>();
            await _conn.InsertAsync(new User(){Id=1, Name = "Bill"});

            //Code that waits for the save to complete and then retrieves the user
        }

I suspect that I need a task somewhere, but im not completely sure how to do this. Thank you

https://msdn.microsoft.com/en-us/library/hh191443.aspx http://www.dotnetperls.com/async http://stackoverflow.com/questions/14455293/async-and-await bunch of example you can look into. — Vinod, Mar 30 '15 at 09:27
I doubt async/await for C# could be around as long as it has without examples of it in many places. As linked by @Vinod, a simple search would have found you these examples and many more. — Lukazoid, Mar 30 '15 at 09:31
You'll want to also await `CreateTableAsync` before awaiting `InsertAsync`. — Jon Hanna, Mar 30 '15 at 09:47

score 7 · Accepted Answer · answered Mar 30 '15 at 09:29

7

You're mostly there already.

When returning void:

public async Task SomethingAsync()
{
    await DoSomethingAsync();
}

When returning a result:

public async Task<string> SomethingAsync()
{
    return await DoSomethingAsync();
}

The thing to note when returning a value in an async method is that you return the inner type (i.e in this case string) rather than a Task<string> instance.

answered Mar 30 '15 at 09:29

Lloyd

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Erm...You should really just do `return DoSomethingAsync();` and drop the `async` from the sig. – Aron Mar 30 '15 at 09:56
@Aron Not if he's awaiting within the method IIRC? – Lloyd Mar 30 '15 at 10:06
No. `DoSomethingAsync()` already returns a `Task`. So you don't need the compiler to unwrap the `Task` `await` it, then wrap the result in another `Task`. – Aron Mar 30 '15 at 10:07

score 1 · Answer 2 · answered Mar 30 '15 at 09:29

1

If your code doesn't return any value, the signature should be this, returning Task:

public async Task SaveToDb()

Else, you would need to specify the return type as the type argument in Task<T>, string in this sample:

public async Task<string> SaveToDb()

answered Mar 30 '15 at 09:29

Patrick Hofman

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Async/await simple example

2 Answers2